1. Field of the Invention
The present invention relates to a sensing device and, more particularly, to a high-efficiency fingerprint identification device.
2. Description of Related Art
The development of electronic commerce promotes the progress of remote payment, in which there is demand for biometrics identification. The technology of biometrics identification includes fingerprint identification, iris identification, DNA identification, and so on. Considering the requirement for efficiency, safety and non-invasion, the fingerprint identification becomes the primary technology in biometrics identification. The fingerprint identification further includes optical type, thermal type, ultrasonic type and capacitance type, wherein the capacitance type stands out in this field by its small size, low cost, power saving, stability and anti-fake function.
The prior capacitance type fingerprint identification technology includes swipe type and touch type, wherein the touch type stands out by its accuracy, efficiency and convenience. However, since the sensing signals are weak and the surrounding noise signals are strong, the touch type fingerprint identification usually integrates the sensing electrodes with the sensing circuits into an integrated circuit chip. In order to prevent the prior fingerprint identification chip from being damaged when packaging, the output wires are protected by a sealant, which separates the sensing electrodes from the fingers by a distance of tens of micrometers (μm), and thus seriously influences the accuracy. Alternatively, the sealant can be replaced by a sapphire film with high dielectric constant, which is however very expensive. Since the distance of tens of micrometers is disadvantageous for product integration, a common method to deal with the problem is to form an opening on the protection glass, and then to embed the fingerprint identification chip into the opening in a complicated way to form a button. This increases the cost of materials and the cost of package manufacturing, and the yield factor, the lifetime and the tolerance of the product are undesirable. Hence, the industry keeps making efforts in improving the sensing sensitivity and the signal to noise ratio, in order to increase the sensing distance between the sensing electrodes and the fingerprint, for simplifying the package of the sensing integrated circuit. It is expected to significantly decrease the cost and increase the lifetime and the tolerance of the product. Therefore, the fingerprint identification technology is desired to be improved.